Two employes of the Grenada embassy here were indicted yesterday by a federal grand jury on charges of smuggling guns out of the U.S. to aid a successful governmental coup in the Caribbean spice island last March.

The indictment, returned by the grand jury here, was immediately denounced by Grenada's ambassador to the U.S. The ambassador, Dessima Williams, said the two defendants are two "prominent" Grenadan citizens who are now counselors at the embassy, and that the indictment comes at a "very unfortunate" time in the development of relations between her country's new government and the United States.

There have been previous reports that the United States apparently has been losing to Cuba in a struggle for influence in the Caribbean island since the March takeover.

Ambassador Williams said after the indictment yesterday that her country had made repeated requests to the U.S. that the charges against the two men accused of gun-running be dropped. She said the two men, "whom we regard as men of high caliber," did no ill or harm to citizens in the U.S. or Grenada.

She said her country viewed the indictment as harmful to developing relations it must now determine how to "reciprocate" in the cases of two U.S. citizens that she said are pending in Grenada. No further details on those two cases were available last night.

Named in the indictment returned here were Chester A. A. Humphrey Jr., 5809 40th Ave., Hyattsville, and James C. Wardally, 144 S. Kossuth St., Baltimore. Wardally formerly lived at 2105 Guilford Rd., Hyattsville.

The indictment, returned after an investigation headed by Assistant U.S. Attorney Douglas Dehr of the major crimes division, accuses the two men of purchasing more than 50 weapons and more than 12,000 rounds of ammunition to be sent to the island.

The weapons -- 48 rifles, one shotgun and four revolvers -- were purchased at various sporting goods stores and gun shops in the Washington area. Virtually all the purchases were of M-1 carbines, which were described in court documents as light military weapons not intended for use in target practice and prohibited as a hunting weapon in Maryland.

Wardally was described in a search warrant affidavit by an Alcohol, Tobacco and Firearms agent as a D.C. cab driver who would purchase the guns and describe himself as a member of the Northwest Black Veterans Rifle Club. No such club exists, according to the AFT agent's affidavit.

The guns were actually secretly shipped to Grenada in 55-gallon drums purchased from oil companies and described in shipping orders as contained only "petroleum oil," investigators said.

The shipments were linked by U.S. investigators to the New Jewel Movement, a socialist regime that rebelled against Sir Eric Gairy in March of this year. Gairy had long run the country as a British colony and then became prime minister when it achieved independence in 1974.

ATF investigators described the Gairy government as including a secret police force known as the "Mongoose Gang", the "night ambush squad" and the "volunteer secret intelligence squad." The leader of the opposition New Jewel movement, and the new leader of the island, is a 34-year-old British-trained attorney, Maurice Bishop.